Base station, communication terminal, transmission method and reception method

ABSTRACT

A base station includes: means configured to manage frequency blocks; means configured to determine, for each frequency block, scheduling information for assigning one or more resource blocks to a communication terminal being in a good channel state; means configured to generate a control channel including the scheduling information for each frequency block; and means configured to frequency multiplexing control channels within the system frequency band and to transmit it. In addition, the base station transmits the control channel by separating a non-specific control channel to be decoded by a non-specific communication terminal and a specific control channel to be decoded by a communication terminal to which one or more resource blocks are assigned.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation and claims benefit, pursuantto 35 U.S.C. §120, to U.S. patent application Ser. No. 12/161,429, filedJul. 18, 2008. That application is hereby incorporated by reference inits entirety.

TECHNICAL FIELD

The present invention relates to a technical field of radiocommunications. More particularly, the present invention relates to abase station, a communication terminal, a transmission method, and areception method used for a communication system in which frequencyscheduling and multicarrier transmission are performed.

BACKGROUND ART

In this kind of technical field, it is becoming more and more importantto realize wideband radio access for performing high speed largecapacity communication efficiently. Especially, as for downlinkchannels, a multicarrier scheme, more particularly, that is anOrthogonal Frequency Division Multiplexing (OFDM) scheme is consideredpromising from the viewpoint of performing high speed large capacitycommunications while suppressing multipath fading effectively, and thelike. Then, performing frequency scheduling is also proposed in a nextgeneration system in terms of improving throughput by increasingfrequency use efficiency.

As shown in FIG. 1, a frequency band that can be used in the system isdivided to a plurality of resource blocks (divided to three blocks inthe example of the figure), and each of the resource blocks includes oneor more subcarriers. The resource block is also called a frequencychunk. A terminal is assigned one or more resource blocks. In frequencyscheduling, a resource block is assigned to a terminal in which channelstate is good by priority according to received signal quality orchannel state information (CQI: Channel Quality Indicator), of each ofresource blocks of a downlink pilot channel, reported from terminals, sothat transmission efficiency or throughput of the whole system is triedto improve. When frequency scheduling is performed, it is necessary toreport content of the scheduling to the terminal, and the report isperformed using a control channel (that may be called L1/L2 controlsignaling channel, associated control channel, low layer controlchannel, or the like). In addition, a modulation scheme (QPSK, 16QAM,64QAM and the like, for example) used for the scheduled resource block,a channel coding information (channel coding rate and the like, forexample), and a hybrid automatic retransmission request (HARQ: HybridAuto Repeat ReQuest) are transmitted using the control channel. Thetechnique for dividing a frequency band into a plurality of resourceblocks and changing modulation schemes for each resource block isdescribed in the non-patent document 1, for example.

Non-Patent Document 1

P. Chow, J. Cioffi, J. Bingham, “A Practical Discrete MultitoneTransceiver Loading Algorithm for Data Transmission over SpectrallyShaped Channel”, IEEE Trans. Commun. vol. 43, No. 2/3/4,February/March/April 1995

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

On the other hand, in a future radio access scheme of next generation,various wide and narrow frequency bands are prepared, so that it may berequired that a terminal can use various bands according to locations orusages. In this case, as to frequency bandwidths that the terminal canreceive, various wide and narrow frequency bands may be preparedaccording to usage or price. Also in this case, if frequency schedulingis properly performed, improvement of frequency use efficiency andthroughput can be expected. However, since the usable frequency bandsfor the existing communication system is predicated on fixed bands, whenvarious wide and narrow frequency bands are provided in the base stationside and the terminal side, a concrete method has not been establishedfor properly reporting content of scheduling to the terminal or the userwhile permitting every combinations.

On the other hand, if a specific resource block common to every terminalis fixedly assigned for a control channel, since channel states ofterminals are generally different for each resource block, there is afear that the control channel cannot be properly received depending onthe terminal. In addition, when the control channel is distributed toall resource blocks, any terminal may receive the control channel with acertain receive quality. But, it becomes difficult to expect receivequality better than that. Therefore, it is desired to transmit a controlchannel to terminals with higher quality.

In addition, when adaptive modulation and coding (AMC) control isperformed in which modulation schemes and channel coding rates areadaptively changed, a number of symbols necessary for transmitting thecontrol channel is different for each terminal. This is because aninformation amount transmitted per one symbol is different depending oncombination in AMC. In addition, in future systems, it is considered totransmit and receive separate signals using a plurality of antennasprovided in each of a transmission side and a receiving side. In thiscase, the before-mentioned control information such as schedulinginformation and the like may be necessary for each of the signalscommunicated by each antenna. Therefore, in this case, the number ofsymbols necessary for transmitting the control channel is different notonly for each terminal, but also, there is a possibility that it isdifferent according to the number of antennas used for the terminal.When an amount of information that should be transmitted using thecontrol channel is different for each terminal, for using resourcesefficiently, it is necessary to use a variable format that can flexiblysupport variation of the control information amount. But, there is afear that signal processing load in the transmitting side and thereceiving side becomes large. In contrast, when the format is fixed, itis necessary to reserve a field specific for the control channeladapting to a maximum information amount. But, by doing that, even ifthe field specific for the control channel is unoccupied, resources ofthat part are not used for data transmission, so that it contradicts therequirement of effective use of resources. Therefore, it is desired totransmit the control channel easily and efficiently.

The present invention is contrived for solving at least one of theabove-mentioned problems, and the object is to provide a base station, acommunication terminal, a transmission method and a reception method forefficiently transmitting a control channel to various terminals in whichbandwidths by which communication can be performed are different, in acommunication system in which a frequency band assigned to thecommunication system is divided into a plurality of frequency blockseach of which includes a plurality of resource blocks each including oneor more subcarriers, and a terminal performs communication using one ormore frequency blocks.

Means for Solving the Problem

A base station using in an embodiment of the present invention is usedin a communication system in which a frequency band provided to thecommunication system includes a plurality of frequency blocks whereineach of the frequency blocks includes a plurality of resource blockseach including one or more subcarriers. The base station communicateswith a communication terminal that uses one or more frequency blocks.The base station includes:

means configured to manage correspondence relationship betweenbandwidths by which individual communication terminals can performcommunication and frequency blocks to be assigned to the communicationterminals;

a frequency scheduler configured to determine, for each frequency block,scheduling information for assigning one or more resource blocks to acommunication terminal being in a good channel state;

means configured to generate a control channel including the schedulinginformation for each frequency block;

multiplexing means configured to frequency multiplexing control channelsgenerated for each frequency block within the frequency band provided tothe communication system; and

means configured to transmit an output signal of the multiplexing meansusing a multicarrier scheme.

A base station used in an embodiment of the present invention is a basestation of a multicarrier scheme that performs frequency scheduling in afrequency band including a plurality of resource blocks each includingone or more subcarriers. The base station includes:

a frequency scheduler configured to determine scheduling information forassigning one or more resource blocks to a communication terminal in agood channel state based on channel state information reported fromindividual communication terminals; and

means configured to perform coding and modulation for a control channelincluding a non-specific control channel to be decoded by a non-specificcommunication terminal and a specific control channel to be decoded by aspecific communication terminal to which one or more resource blocks areassigned;

multiplexing means configured to time multiplexing the non-specificcontrol channel and the specific control channel according to thescheduling information; and

means configured to transmit an output signal of the multiplexing meansusing a multicarrier scheme.

A base station used in an embodiment of the present invention is a basestation of a multicarrier scheme that performs frequency scheduling in afrequency band including a plurality of resource blocks each includingone or more subcarriers. The base station includes:

a frequency scheduler configured to determine scheduling information forassigning one or more resource blocks to a communication terminal in agood channel state based on channel state information reported fromindividual communication terminals;

multiplexing means configured to multiplex a control channel and a datachannel according to the scheduling information; and

means configured to transmit an output signal of the multiplexing meansusing a multicarrier scheme. A control channel to be decoded by aspecific communication terminal is mapped over the frequency bandincluding a plurality of resource blocks in a distributed manner.

A base station used in an embodiment of the present invention is a basestation of a multicarrier scheme that performs frequency scheduling in afrequency band including a plurality of resource blocks each includingone or more subcarriers. The base station includes:

a frequency scheduler configured to determine scheduling information forassigning one or more resource blocks to a communication terminal in agood channel state based on channel state information reported fromindividual communication terminals;

multiplexing means configured to multiplex a control channel and a datachannel according to scheduling information; and

means configured to transmit an output signal of the multiplexing meansusing a multicarrier scheme. A control channel to be decoded by aspecific communication terminal is mapped limitedly to a resource blockassigned to the specific communication terminal.

A base station used in an embodiment of the present invention is a basestation of a multicarrier scheme that performs frequency scheduling in afrequency band including a plurality of resource blocks each includingone or more subcarriers. The base station includes:

a frequency scheduler configured to determine scheduling information forassigning one or more resource blocks to a communication terminal in agood channel state based on channel state information reported fromindividual communication terminals; and

means configured to perform coding and modulation for a control channelincluding a non-specific control channel to be decoded by a non-specificcommunication terminal and a specific control channel to be decoded by aspecific communication terminal to which one or more resource blocks areassigned;

multiplexing means configured to time multiplex the non-specific controlchannel and the specific control channel according to the schedulinginformation; and

means configured to transmit an output signal of the multiplexing meansusing a multicarrier scheme. The non-specific control channel includesinformation indicating a transmission format of the non-specific controlchannel.

Effect of the Invention

According to the present invention, it becomes possible to efficientlytransmit a control channel to various terminals in which bandwidths bywhich communication can be performed are different, in a communicationsystem in which each of a plurality of frequency blocks forming a systemfrequency band includes a plurality of resource blocks each includingone or more subcarriers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining frequency scheduling;

FIG. 2 is a diagram showing a frequency band used in an embodiment ofthe present invention;

FIG. 3A shows a partial block diagram of a base station according to anembodiment of the present invention (1);

FIG. 3B shows a partial block diagram of a base station according to anembodiment of the present invention (2);

FIG. 4A is a diagram showing signal processing elements on one frequencyblock;

FIG. 4B is a diagram showing signal processing elements on a controlchannel;

FIG. 4C is a diagram showing signal processing elements on a controlchannel;

FIG. 4D is a diagram showing signal processing elements on a controlchannel;

FIG. 4E is a diagram showing signal processing elements on one frequencyblock;

FIG. 5A is a diagram showing information item examples of controlsignaling channels;

FIG. 5B is a diagram showing a localized FDM scheme and a distributedFDM scheme;

FIG. 5C is a diagram showing a L1/L2 control channel in which a numberof symbols changes according to a number of simultaneously multiplexedusers;

FIG. 6 is a diagram showing units of error correcting coding;

FIG. 7A is a diagram showing a mapping example of data channels andcontrol channels;

FIG. 7B is a diagram showing a mapping example of data channels andcontrol channels;

FIG. 7C is a diagram showing format examples of the L1/L2 controlchannel;

FIG. 7D is a diagram showing format examples of the L1/L2 controlchannel;

FIG. 7E is a diagram showing mapping examples of the L1/L2 controlchannel in a three sector configuration;

FIG. 7F is a diagram exemplary showing multiplexing schemes of anon-specific control channel;

FIG. 7G is a diagram showing a mapping example of data channels andcontrol channels;

FIG. 7H is a diagram showing a mapping example of data channels andcontrol channels;

FIG. 7I is a diagram showing a mapping example of data channels andcontrol channels;

FIG. 7J is a diagram showing a manner for grouping users in a cell;

FIG. 8A shows a partial block diagram of a terminal used in anembodiment of the present invention;

FIG. 8B shows a partial block diagram of a terminal used in anembodiment of the present invention;

FIG. 8C shows a block diagram related to a reception unit of theterminal;

FIG. 9 is a flowchart showing an operation example according to anembodiment of the present invention;

FIG. 10A is a diagram showing relationship between subjects of errorcheck and channel coding units;

FIG. 10B is a diagram showing relationship between subjects of errorcheck and channel coding units;

FIG. 10C is a diagram showing relationship between subjects of errorcheck and channel coding units;

FIG. 10D is a diagram showing a method example for decreasinginformation amount of uplink data transmission related information;

FIG. 10E is a diagram showing an operation example when frequencyhopping is performed;

FIG. 11 is a diagram showing a flowchart of an operation example andfrequency bands of an embodiment of the present invention;

FIG. 12 is a diagram showing a flowchart of another operation exampleand frequency bands of an embodiment of the present invention;

FIG. 13 is a diagram showing a manner in which TPC is performed;

FIG. 14 is a diagram showing a manner in which AMC control is performed.

DESCRIPTION OF REFERENCE SIGNS

-   31 frequency block assignment control unit-   32 frequency scheduling unit-   33-x control signaling channel generation unit in frequency block x-   34-x data channel generation unit n frequency block x-   35 broadcast channel (or paging channel) generation unit-   1-x first multiplexing unit on frequency block x-   37 second multiplexing unit-   38 third multiplexing unit-   39 other channel generation unit-   40 Inverse Fast Fourier Transform unit-   41 cyclic prefix adding unit-   41 non-specific control channel generation unit-   42 specific control channel generation unit-   43 multiplexing unit-   81 carrier frequency tuning unit-   82 filtering unit-   83 cyclic prefix removing unit-   84 fast Fourier transform unit (FFT)-   85 CQI measurement unit-   86 broadcast channel decoding unit-   87-0 non-specific control channel (part 0) decoding unit-   87 non-specific control channel decoding unit-   88 specific control channel decoding unit-   89 data channel decoding unit

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

According to an embodiment of the present invention, frequencyscheduling is performed for each frequency, and the control channel forreporting scheduling information is generated for each frequency blockin accordance with a minimum bandwidth. Accordingly, the control channelcan be efficiently transmitted to various communication terminals inwhich bandwidths by which communication can be performed are different.The communication terminal is a mobile terminal or a mobile stationtypically, but it may be a fixed terminal or a fixed station. Thecommunication terminal may be called a user apparatus.

The control channels generated for each frequency block may be frequencymultiplexed according to a predetermined hopping pattern. This canequalize communication quality among communication terminals and amongfrequency blocks.

A broadcast channel may be transmitted using a band that is a bandincluding a center frequency of the frequency band provided to thecommunication system and that has a bandwidth corresponding to onefrequency block. This allows any communication terminal that tries toaccess the communication system to easily connect to the communicationsystem by receiving a signal of a minimum bandwidth in the vicinity ofthe center frequency.

A paging channel is also transmitted using a band that is a bandincluding a center frequency of the frequency band provided to thecommunication system and that has a bandwidth corresponding to onefrequency block. This makes it possible to combine a reception band whenstandby and a band for performing cell search, so that this ispreferable from the viewpoint that a number of times of frequency tuningcan be decreased as much as possible.

From the viewpoint of using the whole frequency band evenly, a pagingchannel for paging a communication terminal may be transmitted using afrequency block assigned to the communication terminal.

According to an embodiment of the present invention, the control channelmay be separated to a non-specific control channel to be decoded by anon-specific communication terminal and a specific control channel to bedecoded by a specific communication terminal to which one or moreresource blocks are assigned, and these channels may be coded andmodulated separately. The non-specific control channel and the specificcontrol channel are time multiplexed according to scheduling informationso that the control channel is transmitted using a multicarrier scheme.Accordingly, the control channel can be efficiently transmitted withoutwaste of resources using a fixed format even though control informationamounts are different for each communication terminal.

The non-specific control channel may be mapped over the frequency bandin a distributed manner, and the specific control channel relating to aspecific communication terminal may be mapped limitedly to a resourceblock assigned to the specific communication terminal. While the qualityof the non-specific control channel can be kept to be equal to orgreater than a certain level over the whole users, the quality of thespecific control channel can be made good. This is because the specificcontrol channel is mapped to a resource block in a good channel statefor each of the specific communication terminals.

A downlink pilot channel may be also mapped over a plurality of resourceblocks assigned to a plurality of communication terminals in adistributed manner. By mapping the pilot channel over a wide band,channel estimation accuracy and the like can be improved.

According to an embodiment of the present invention, from the viewpointof maintaining or improving reception quality of the control channelincluding the non-specific and specific control channels, transmissionpower control is performed on the non-specific control channel, and oneor both of transmission power control and adaptive modulation and codingcontrol are performed on the specific control channel.

Transmission power control for the non-specific control channel may beperformed such that the specific communication terminal to which aresource block is assigned can receive the non-specific control channelwith high quality. This is because, although every user or communicationterminal that received the non-specific control channel is obliged totry demodulation, it is only necessary that the user to which a resourceblock is actually assigned succeeds demodulation eventually.

The non-specific control channel may include information of one or bothof a modulation scheme and a coding scheme applied to the specificcontrol channel. Since the combination of the modulation scheme and thecoding scheme for the non-specific control channel is fixed, the user towhich the resource block is assigned can obtain the modulation schemeand the coding scheme and the like for the specific control channel bydemodulating the non-specific control channel. By this method, adaptivemodulation and coding control can be performed on the part of thespecific control channel in the control channel, so that receptionquality of the part can be improved.

When the transmission power control and the adaptive modulation andcoding control are performed for the control channel, a total number ofcombinations of modulation schemes and coding schemes for the specificcontrol channel may be prepared to be less than a total number ofcombinations of modulation schemes and coding schemes for the shareddata channel. This is because, although required quality can be obtainedby the adaptive modulation and coding control, required quality can beobtained by performing transmission power control.

Embodiment 1

FIG. 2 shows a frequency band used in an embodiment of the presentinvention. Although concrete numeric values are used for the sake ofdescription, the values are merely examples, and various values may beused. The frequency band (whole transmission band) provided for thecommunication system has a bandwidth of 20 MHz as an example. The wholetransmission band includes four frequency blocks 1-4, and each of thefrequency blocks includes a plurality of resource blocks each includingone or more subcarriers. The example shown in the figure schematicallyshows that each frequency block includes many subcarriers. In thepresent embodiment, four types of 5 MHz, 10 MHz, 15 MHz and 20 MHz areprepared as bandwidths for performing communication. A terminal uses oneor more frequency blocks to perform communication using one of the fourbandwidths. A terminal performing communication in the communicationsystem may be able to perform communication by using any of the fourbands, or may be able to perform communication by using only some of thebandwidths. However, it is necessary to be able to perform communicationusing at least 5 MHz band. Or, instead of preparing such a plurality ofkinds of bands, a standard may be defined such that any communicationterminal can perform communication in the whole of the system bandwidth.For providing more general description, a case in which choices of fourkinds of bandwidths are prepared in the following embodiments isdescribed. However, it can be understood that the present invention isapplicable irrespective of presence or absence of such choices of thebandwidths.

In the present embodiment, a control channel (L1/L2 control signalingchannel or low layer control channel) for reporting schedulinginformation of a data channel (shared data channel) is formed by theminimum bandwidth (5 MHz), and the control channel is independentlyprovided for each frequency block. For example, when a terminalperforming communication using a bandwidth of 5 MHz performscommunication using a frequency block 1, the terminal receives a controlchannel prepared for the frequency block 1 so that the terminal canobtain content of scheduling. Which frequency block the terminal can usefor communication may be reported beforehand using a broadcast channel,for example. In addition, after starting communication, a frequencyblock to be used may be changed. When a terminal performingcommunication using a bandwidth of 10 MHz performs communication usingfrequency blocks 1 and 2, the terminal uses adjacent two frequencyblocks, and receives both control channels prepared for the frequencyblocks 1 and 2 so that the terminal can obtain content of schedulingover a range of 10 MHz. A terminal that performs communication using abandwidth of 15 MHz uses adjacent three frequency blocks, and when theterminal performs communication using frequency blocks 1, 2 and 3, theterminal receives all control channels prepared for the frequency blocks1, 2 and 3 so that the terminal can obtain content of scheduling overthe range of 15 MHz. A terminal that performs communication using abandwidth of 20 MHz receives all control channels provided for allfrequency blocks so that the terminal can obtain content of schedulingover the range of 20 MHz.

In the figure, four discrete blocks are shown in a frequency block withrespect to the control channel. This shows that the control channel isdistributed and mapped into a plurality of resource blocks in thefrequency block. A concrete mapping example of the control channel isdescribed later.

FIG. 3A shows a partial block diagram of a base station according to anembodiment of the present invention. FIG. 3A shows a frequency blockassignment control unit 31, a frequency scheduling unit 32, a controlsignaling channel generation unit 33-1 and a data channel generationunit 34-1 in the frequency block 1, . . . , a control signaling channelgeneration unit 33-M and a data channel generation unit 34-M in thefrequency block M, a broadcast channel (or paging channel) generationunit 35, a first multiplexing unit 1-1 for the frequency block 1, . . ., a first multiplexing unit 1-M for the frequency block M, a secondmultiplexing unit 37, a third multiplexing unit 38, an other channelgeneration unit 39, an Inverse Fast Fourier Transform unit 40 (IFFT) anda cyclic prefix adding unit 41.

Based on information relating to a maximum bandwidth by whichcommunication can be performed reported from a terminal (that may be amobile terminal or a fixed terminal), the frequency block assignmentcontrol unit 31 checks a frequency block to be used by the terminal. Thefrequency block assignment control unit 31 manages correspondencerelationship between individual terminals and frequency blocks, andreports the content to the frequency scheduling unit 32. Which frequencyblock can be used for communication by a terminal that can performcommunication using a bandwidth may be reported beforehand using abroadcast channel. For example, the broadcast channel may permit a userperforming communication using the bandwidth of 5 MHz to use any oneband of frequency blocks 1, 2, 3 and 4, or use may be limited to any ofthese. In addition, a user that performs communication using a bandwidthof 10 MHz is permitted to use a combination of adjacent two frequencyblocks such as frequency blocks (1, 2), (2, 3) or (3, 4). All of thesemay be permitted to use, or use may be limited to any one of thecombinations. A user that performs communication using a bandwidth of 15MHz is permitted to use a combination of adjacent three frequency blockssuch as frequency blocks (1, 2, 3) or (2, 3, 4). Both of them may bepermitted to use, or use may be limited to any one of the combinations.A user that performs communication using a bandwidth of 20 MHz ispermitted to use all of the frequency blocks. As described later, ausable frequency block may be changed after starting communicationaccording to a predetermined frequency hopping pattern.

The frequency scheduling unit 32 performs frequency scheduling in eachof the plurality of frequency blocks. Frequency scheduling in onefrequency block determines scheduling information so as to assign aresource block preferentially to a terminal having a good channel statebased on channel state information CQI of each resource block reportedfrom terminals.

The control signaling channel generation unit 33-1 in the frequencyblock 1 uses resource blocks only in the frequency block 1 to configurea control signaling channel for reporting scheduling information in thefrequency block 1 to terminals. Similarly, as to other frequency block,a control signaling channel for reporting scheduling information in thefrequency block to terminals is configured using resource blocks only inthe frequency block.

The data channel generation unit 34-1 in the frequency block 1 generatesa data channel to be transmitted using one or more resource blocks inthe frequency block 1. Since the frequency block 1 may be shared by oneor more terminals (users), N data channel generation units 1-1-N areprepared in the example shown in the figure. Similarly, as to otherfrequency block, data channels of terminals that share the frequencyblock are generated.

A first multiplexing unit 1-1 for the frequency block 1 multiplexessignals relating to the frequency block 1. This multiplexing at leastincludes frequency multiplexing. How the control signaling channel andthe data channel are multiplexed is described later. Similarly, otherfirst multiplexing unit 1-x multiplexes the control signaling channeland the data channel transmitted using the frequency block x.

The second multiplexing unit 37 performs operation for changing positionrelationship among the various multiplexing units 1-x (x=1, . . . , M)on the frequency axis according to a predetermined hopping pattern. Thisfunction is described in the second embodiment.

The broadcast channel (or paging channel) generation unit 35 generatesbroadcast information such as office data to be reported to terminalsunder the base station. Information indicating relationship between amaximum frequency band by which the terminal can perform communicationand a frequency block that the terminal can use may be included incontrol information. When the usable frequency block variously changes,the broadcast information may include information specifying a hoppingpattern that indicates how the frequency block changes. By the way, thepaging channel may be transmitted using a same band as the broadcastchannel, or may be transmitted using a frequency block used in eachterminal.

Other channel generation unit 39 generates a channel other than thecontrol signaling channel and the data channel. For example, the otherchannel generation unit 39 generates a pilot channel. A pilot channel ora pilot signal is some sort of proper signal that is known in thetransmission side and the reception side, and it may be referred to as areference signal, a reference signal, a known signal, a training signaland the like.

The third multiplexing unit 38 multiplexes the control signalingchannels and the data channels of each frequency block, and, thebroadcast channel and/or other channel as necessary.

The Inverse fast Fourier transform unit 40 performs inverse fast Fouriertransform on a signal output from the third multiplexing unit 38 toperform modulation based on the OFDM scheme.

The cyclic prefix (CP) adding unit 41 adds a guard interval to a symbolafter modulation of the OFDM scheme to generate a transmission symbol.The transmission symbol may be generated by adding a series of data atthe end (or top) of the OFDM symbol to the top (or end).

FIG. 3B shows elements next to the CP adding unit 41 shown in FIG. 3A.As shown in the figure, the symbol to which the guard interval is addedis amplified to a proper power by a power amplifier after processes ofdigital analog conversion, frequency conversion and band limitation andthe like by an RF transmission circuit, and the signal is transmittedvia a duplexer and a transmit and receive antenna.

Although not essential for the present invention, antenna diversityreception is performed by two antennas when performing reception in thepresent embodiment. An uplink signal received by the two antennas aresupplied to an uplink signal reception unit.

FIG. 4A shows signal processing elements on one frequency block (x-thfrequency block). “x” is an integer equal to or greater than 1 and equalto or less than M. Generally, the figure shows a control signalingchannel generation unit 33-x and a data channel generation unit 34-xrelating to the frequency block x, multiplexing units 43-A and B, and amultiplexing unit 1-x. The control signaling channel generation unit33-x includes a non-specific control channel generation unit 41 and oneor more specific control channel generation units 42-A, B, . . . .

In the control signaling channel, the non-specific control channelgeneration unit 41 performs channel coding and multilevel modulation ona part of the non-specific control channel (that may be callednon-specific control information) that every terminal using thefrequency block should decode and demodulate, and outputs it.

Each of the specific control channel generation units 42-A, B, . . .performs channel coding and multilevel modulation on a part of thespecific control channel (that may be called specific controlinformation), in the control signaling channel, that a terminal to whichone or more resource blocks is assigned in the frequency block shoulddecode and demodulate, and outputs it.

The data channel generation units x-A, B, . . . perform channel codingand multilevel modulation on data channels addressed to individualterminals A, B, . . . , respectively. Information on the channel codingand multilevel modulation is included in the specific control channel.

The multiplexing unit (43-A, B, . . . ) associates the specific controlchannel and the data channel to a resource block for each terminal towhich the resource block is assigned.

As mentioned above, coding (and modulation) for the non-specific controlchannel is performed in the non-specific control channel generation unit41, and coding (and modulation) for the specific control channel isperformed in the specific control channel generation units 42-A, B, . .. , individually. Therefore, in the present embodiment, as shown in FIG.6 conceptually, the non-specific control channel includes pieces ofinformation of all users to whom the frequency block x is assigned, andthese pieces of information become a subject for error correcting codingon the whole.

In another embodiment, the non-specific control channel may be alsoerror correcting coded for each user. In this case, since each usercannot uniquely specify which block includes its own information inblocks that are individually error correcting coded, it is necessary todecode all blocks. In this another embodiment, since coding processingis closed for each user, it is relatively easy to add and change users.Each user needs to decode and modulate non-specific control channels ofall users.

On the other hand, the specific control channel only includesinformation on a user to which a resource block is actually assigned, sothat error correcting coding is performed for each user. Which user isassigned a resource block is revealed by decoding and modulating thenon-specific control channel. Therefore, it is not necessary that alluser decode the specific control channel, and it is only necessary thata user to which a resource block is assigned perform decoding. By theway, a channel coding rate and a modulation scheme for the specificcontrol channel are changed as necessary during communication, but achannel coding rate and a modulation scheme for the non-specific controlchannel may be fixed. However, it is desirable to perform transmissionpower control (TPC) for ensuring signal quality equal to or greater thana given level. The specific control channel is transmitted using a goodresource block after error correcting coding is performed. Therefore,downlink data amount may be decreased to some extent by performingpuncturing.

FIG. 5A shows an example of types and information items of downlinkcontrol signaling channels. The downlink control signaling channelsinclude a broadcast channel (BCH), an individual L3 signaling channel(upper layer control channel or high layer control channel) and a L1/L2control channel (low layer control channel). The L1/L2 control channelmay include not only information for downlink data transmission but alsoinformation for uplink data transmission. In the following, outlines ofinformation items transmitted by each channel are described.

(Broadcast Channel)

The broadcast channel is used for reporting unchanging information orinformation changing at a low speed in a cell to a communicationterminal (that may be a mobile terminal or a fixed terminal, or may becalled a user apparatus). For example, information that may change in aperiod of about 1000 ms (1 second) may be reported as broadcastinformation. The broadcast information may include a transmission formatof a downlink L1/L2 control channel, a maximum number of users assignedsimultaneously, resource block placement information and MIMO schemeinformation.

The transmission format is specified by a data modulation scheme and achannel coding rate. Instead of the channel coding rate, data size maybe reported. This is because the channel coding rate can be uniquelyderived from the data modulation scheme and the data size.

The maximum number of simultaneously assigned users indicates a maximumnumber that can be multiplexed in 1TTI using one or more of FDM, CDM andTDM. The number may be the same or may be different between the uplinkchannel and the downlink channel.

The resource block placement information is information for specifyingpositions of resource blocks on frequency and time axes used in thecell. In the present embodiment, as the frequency division multiplex(FDM) scheme, two kinds that are a localized FDM scheme and adistributed FDM scheme can be used. In the localized FDM scheme,continuous bands are locally assigned to a user in a good channel stateon the frequency axis on a priority basis. This scheme is advantageousfor communication of a user of small mobility, data transmission of highquality and high capacity, and the like. In the distributed FDM scheme,a downlink signal is generated so as to intermittently include aplurality of frequency components ranging over a wide band. This schemeis advantageous for communication of a user of large mobility, periodicdata transmission of small data size such as voice packet (VoIP), andthe like. Whether any scheme is used, resource assignment for frequencyresources is performed according to information specifying continuousbands or a plurality of discrete frequency components.

As shown in the upper side of FIG. 5B, when a resource is specified by“4” in the localized FDM scheme, for example, a resource of the physicalresource block number 4 is used. In the distributed FDM scheme shown inthe lower side of FIG. 5B, when a resource is specified by “4”, two lefthalves of physical resource blocks 2 and 8 are used. In the exampleshown in the figure, one physical resource block is divided into two.Numbering and the number of divisions in the distributed FDM scheme maydifferent for each cell. Thus, resource block placement information isreported to communication terminals in the cell by the broadcastchannel.

When a plurality of antennas are provided in a base station, MIMO schemeinformation indicates which is performed among a single user MIMO(SU-MIMO:Single User-Multi Input Multi Output) scheme or a multi userMIMO (MU-MIMO:Multi-User MIMO) scheme. The SU-MINO scheme is a schemefor communicating with one communication terminal having a plurality ofantennas, and the MU-MIMO scheme is a scheme for communicating with aplurality of communication terminals each having one antennasimultaneously.

(Individual L3 Signaling Channel)

The individual L3 signaling channel is also used for reporting, to acommunication terminal, information that changes at low speed such as ina period of 1000 ms, for example. Although the broadcast channel is sentto all communication terminals in the cell, the individual L3 signalingchannel is sent only to a specific communication terminal. Theindividual L3 signaling channel includes a type of the FDM scheme andpersistent scheduling information. The individual L3 signaling channelmay be also classified to the specific control channel.

The type of the FDM scheme specifies which of the localized FDM schemeand the distribute FDM scheme is used for multiplexing the specifiedindividual communication terminals.

The persistent scheduling information specifies, when persistentscheduling is performed, a transmission format (data modulation schemeand channel coding rate) of uplink or downlink data channel, a resourceblock to be used, and the like.

(L1/L2 Control Channel)

The downlink L1/L2 control channel may include not only informationrelated to downlink data transmission but also information related touplink data transmission. The former can be classified into part 0, part1, part 2 a and part 2 b. The part 1 and the part 2 a can be classifiedas the non-specific control channel, and the part 2 b is classified asthe specific control channel.

(Part 0)

Part 0 includes information indicating a transmission format of theL1/L2 control channel (modulation scheme and channel coding rate, and anumber of simultaneously assigned users or a number of the whole controlbits). When the transmission format of the L1/L2 control channel isreported by the broadcast channel, part 0 may include the number ofsimultaneously assigned users (or the number of the whole control bits).

A number of symbols necessary for L1/L2 control channel depends on thenumber of simultaneously multiplexed users and reception quality ofmultiplexed users. As shown in the left side of FIG. 5C, the number ofsymbols of the L1/L2 control channel is set to be large enoughtypically. When changing the number of symbols, it can be controlled ina period of about 1000 ms (1 second), for example, according to thetransmission format of the L1/L2 control channel reported by thebroadcast channel. However, when the number of the simultaneouslymultiplexed users is small as shown in the right side of FIG. 5C, thenumber of symbols necessary for the control channel becomes small.Therefore, when the number of the simultaneously assigned users and thereception quality of the multiplexed users change in a short period,there is a case in which waste occurs in the L1/L2 control channel thatis prepared large enough.

To decrease the waste of the L1/L2 control channel, the modulationscheme, the channel coding rate, and the number of simultaneouslyassigned users (or the number of the whole control bits) may be reportedin the L1/L2 control channel. By reporting the modulation scheme and thechannel coding rate in the L1/L2 control channel, the modulation schemeand the channel coding rate can be changed with a shorter period thanthat in reporting by the broadcast channel.

(Part 1)

Part 1 includes a paging indicator (PI). Each communication terminaldemodulates the paging indicator so as to be able to check whetherpaging for the own terminal is performed.

(Part 2 a)

Part 2 a includes resource assignment information of a downlink datachannel, assigned time length, and MIMO information.

The resource assignment information of the downlink data channelspecifies a resource block including the downlink data channel. Variousmethods known in this technical field can be used for specifying theresource block. For example, bit map scheme, tree branching numberscheme and the like may be used.

The assignment time length indicates how long the downlink data channelis continuously transmitted. Changing the resource assignment contentmost frequently corresponds to changing it every TTI. From a viewpointto decrease overhead, the data channel may be transmitted with sameresource assignment content over a plurality of TTIs.

The MIMO information specifies, when the MIMO scheme is used forcommunication, a number of antennas, a number of streams, and the like.The number of streams may be called a number of information series.

By the way, although it is not essential that the part 2 a include useridentification information, the whole or a part of it may be included.

(Part 2 b)

Part 2 b includes precoding information when the MIMO scheme is used,transmission format of the downlink data channel, hybrid retransmissioncontrol (HARQ) information and CRC information.

The precoding information when the MIMO scheme is used specifiesweighting coefficients applied to each of a plurality of antennas. Byadjusting the weighting coefficients applied to each antenna,directivity of a communication signal is adjusted.

The transmission format of the downlink data channel is specified by thedata modulation scheme and the channel coding rate. Instead of thechannel coding rate, data size or payload size may be reported. This isbecause the channel coding rate can be uniquely derived from the datamodulation scheme and the data size.

The hybrid retransmission control (HARQ: Hybrid Automatic RepeatRequest) information includes information necessary for retransmissioncontrol for downlink packets. More particularly, the retransmissioncontrol information includes process number, redundancy versioninformation indicating packet combining method, and new data indicatorfor distinguishing between a new packet and a retransmission packet.

The CRC information indicates, when a cyclic redundancy check method isused for error detection, CRC detection bit in which user identificationinformation (UE-ID) is convoluted.

Information related to uplink data transmission can be classified into 4types from part 1 to part 4 as follows. Although these pieces ofinformation may be classified to the non-specific control channel inprinciple, they may be transmitted as a specific control channel for acommunication terminal to which resource is assigned for a downlink datachannel.

(Part 1)

Part 1 includes transmission confirmation information for a past uplinkdata channel. The transmission confirmation information indicatesacknowledgment (ACK) indicating that there is no error in the packet orthat there is an error but it is in a permissible range, or indicatesnegative acknowledgment (NACK) indicating that there is an errorexceeding a permissible range in a packet.

(Part 2)

Part 2 includes resource assignment information for a future uplink datachannel, transmission format of the uplink data channel, transmissionpower information and CRC information.

The resource assignment information specifies a resource block that canbe used for transmitting an uplink data channel. For specifying theresource block, various methods that are known in this technical fieldcan be used. For example, bitmap scheme, tree branching number scheme,and the like may be used.

The transmission format of the uplink data channel is specified by thedata modulation scheme and the channel coding rate. Instead of thechannel coding rate, data size or payload size may be reported. This isbecause the channel coding rate can be uniquely derived from the datamodulation scheme and the data size.

The transmission power information indicates how large a power by whichthe uplink data channel should be transmitted is.

The CRC information indicates, when a cyclic redundancy check method isused for error detection, CRC detection bit in which user identificationinformation (UE-ID) is convoluted. By the way, in a response signal(downlink L1/L2 control channel) for a random access channel (RACH), arandom ID of RACH preamble may be used as UE-ID.

(Part 3)

In part 3, a transmission timing control bit is included. This is acontrol bit for synchronizing the communication terminals in a cell.

(Part 4)

Part 4 includes transmission power information on transmission power ofa communication terminal. This information indicates how large is apower which the communication terminal, to which a resource is notassigned for transmitting uplink data channel, should use fortransmitting an uplink control channel for reporting CQI of a downlinkchannel, for example.

Similarly to FIG. 4A, FIG. 4E shows signal processing elements on onefrequency block. But, it appears different from FIG. 4A in that itconcretely shows respective pieces of control information. In FIGS. 4Aand 4E, same reference symbols indicate same elements. In the figure,“mapping within resource block” indicates that mapping is performedbeing limited to one or more resource blocks assigned to a specificcommunication terminal. “Mapping outside resource block” indicates thatmapping is performed over the whole region of the frequency blockincluding many resource blocks. Information (parts 1-4) related touplink data transmission in the L1/L2 control channel is transmitted,when a resource is assigned for a downlink data channel, using theresource as a specific control channel, and the information istransmitted, when the resource is not assigned, over the whole frequencyblock as a non-specific control channel.

FIG. 7A shows a mapping example of data channels and control channels.The mapping example shown in the figure is for one frequency block andfor one subframe, and generally corresponds to output content of thefirst multiplexing unit 1-x (pilot channel and the like is multiplexedby the third multiplexing unit 38). One subframe may correspond to onetransmission time interval (TTI), or correspond to a plurality of TTIs,for example. In the example shown in the figure, the frequency blockincludes seven resource blocks RB1-7. The seven resource blocks areassigned to terminals having a good channel state by the frequencyscheduling unit 32 shown in FIG. 3A.

In general, the non-specific control channel and the like, the pilotchannel and the like, and the data channel and the like are timemultiplexed. The non-specific control channel is mapped all over thefrequency block in a distributed manner. That is, the non-specificcontrol channel is distributed all over the band occupied by sevenresource blocks. In the example shown in the figure, the non-specificcontrol channel and other control channels (excluding specific controlchannel) are frequency multiplexed. Other channels may include asynchronization channel and the like, for example (the non-specificcontrol channel may be defined so as to include the synchronizationchannel and the like without differentiating between the non-specificcontrol channel and the other control channels). In the example shown inthe figure, the non-specific control channel and the other controlchannel are frequency multiplexed such that each includes a plurality offrequency components that are arranged at certain intervals. Suchmultiplexing scheme is called distributed frequency division multiplex(FDM) scheme. The intervals between the frequency components may be thesame or may be different. In any case, it is necessary that thenon-specific control channel is distributed over the whole range of onefrequency block.

In the example shown in the figure, a pilot channel and the like is alsomapped over the whole range of the frequency block. From the viewpointof correctly performing channel estimation and the like for variousfrequency components, it is desirable that the pilot channel is mappedover a wide range as shown in the figure.

In the example shown in the figure, resource blocks RB1, RB2 and RB4 areassigned to a user 1 (UE1), resource blocks RB3, RB5 and RB6 areassigned to a user 2 (UE2), and a resource block RB7 is assigned to auser 3 (UE3). As mentioned above, such assignment information isincluded in the non-specific control channel. In addition, a specificcontrol channel on the user 1 is mapped to the head of the resourceblock RB1 in the resource blocks assigned to the user 1. A specificcontrol channel on the user 2 is mapped to the head of the resourceblock RB3 in the resource blocks assigned to the user 2. A specificcontrol channel on the user 3 is mapped to the head of the resourceblock RB7 in the resource block assigned to the user 3. In the figure,it should be noted that sizes occupied by the specific control channelof the users 1, 2 and 3 are shown to be uneven. This indicates thatinformation amount of the specific control channel may differentaccording to users. The specific control channel is locally mappedlimitedly to a resource block assigned to the data channel. In thispoint, this scheme is different from the distributed FDM in whichmapping is performed over various resource blocks in a distributedmanner. Such a mapping scheme is also called a localized frequencydivision multiplexing (localized FDM).

FIG. 7B shows another mapping example of the non-specific controlchannel. Although the specific control channel of the user 1 (UE1) ismapped only to one resource block RB1 in FIG. 7A, it is discretelymapped over the whole of the resource blocks RB1, RB2 and RB4 (the wholeof the resource blocks assigned to user 1) in a distributed manner usingthe distributed FDM scheme. In addition, the specific control channel onthe user 2 (UE2) is also different from the case shown in FIG. 7A, andit is mapped over the whole of the resource blocks RB3, RB5 and RB6. Thespecific control channel and the shared data channel of the user 2 aretime division multiplexed. Accordingly, the specific control channel andthe shared data channel of each user may be multiplexed using timedivision multiplexing (TDM) scheme and/or frequency divisionmultiplexing scheme (including localized FDM scheme and distributed FDMscheme) in all or a part of one or more resource blocks assigned to theuser. By mapping the specific control channel over equal to or greaterthan two resource blocks, frequency diversity effect can be expectedalso for the specific control channel, so that signal quality of thespecific control channel can be further improved.

Next, concrete formats of the part 0 in the L1/L2 control channel aredescribed.

FIG. 7C is an example showing formats of the L1/L2 control channel whenreporting a number of symbols (or simultaneously assigned user number)of the L1/L2 control channel. When the communication terminal uses amodulation scheme and a coding rate (MCS: Modulation and Coding Scheme)reported by the broadcast channel, the number of symbols necessary forthe L1/L2 control channel changes according to the number ofsimultaneously assigned users. For identifying it, control bits (twobits in FIG. 7C) are provided as information of the part 0 of the L1/L2control channel. For example, by reporting control bits of 00 asinformation of the part 0, for example, the communication terminal canascertain that the number of symbols of the L1/L2 control channel is 100by decoding the control bits. By the way, the head two bits in FIG. 7Ccorresponds to the part 0, and variable control channel correspond tothe non-specific control channel (corresponding to part 1 and part 2 ain the case of downlink). In addition, although MCS is reported by thebroadcast channel in FIG. 7C, MCS may be reported by a L3 signalingchannel.

FIG. 7D is an example showing a format of the L1/L2 control channel whenthe number of simultaneously assigned users of each MCS is reported bypart 0. When using a proper MCS from predetermined kinds of MCSesaccording to reception quality of the communication terminal, the numberof symbols necessary for the L1/L2 control channel changes according tothe reception quality of the communication terminal. For identifyingthis, control bits (eight bits in FIG. 7D) is provided as information ofpart 0 of the L1/L2 control channel. FIG. 7D shows a case, as anexample, in which there are four kinds of MCSes and a maximum value ofthe number of simultaneously assigned users of each MCS is three. Sincethe number of simultaneously assigned users is 0-3, this information canbe represented by two bits (00=0 user, 01=1 user, 10=2 users, 11=3users). Since two bits are necessary for each MCS, part 0 becomes eightbits in this case. For example, by reporting control bits of 01100001 asinformation of the part 0, the communication terminal can ascertaincontrol information (part 2 a in the case of downlink) according to theown reception quality based on the control bits.

FIG. 7E is an example showing mapping of information bits (part 0) inthe L1/L2 control channel in the case of three sector configuration. Inthe case of three sector configuration, three kinds of patterns may beprepared for transmitting the information bits (part 0) indicating atransmission format of the L1/L2 control channel, and assigned to eachsector such that the patterns do not overlap in the frequency domain. Byselecting a pattern such that transmission patterns in adjacent sectors(or cells) are different with each order, effect of interferencecoordination can be obtained.

FIG. 7F shows various examples of multiplexing methods. Although variousnon-specific control channels are multiplexed using the distributed FDMscheme in the above-mentioned examples, various proper multiplexingmethods such as code division multiplexing scheme and time divisionmultiplexing (TDM) scheme may be used. FIG. 7F(1) shows a case in whichmultiplexing is performed by the distributed FDM scheme. By usingnumbers 1, 2, 3 and 4 specifying a plurality of discrete frequencycomponents, signals of each user can be properly orthogonalized.However, it is not necessary to be arranged regularly like this example.In addition, by using different rules between adjacent cells,interference amount when performing transmission power control can berandomized. FIG. 7F(2) shows a case in which multiplexing is performedby code division multiplexing (CDM) scheme. By using code 1, 2, 3 and 4,signals of each user can be properly orthogonalized. FIG. 7F(3) shows acase when the user multiplexing number changes to three in thedistributed FDM scheme. By re-defining the numbers 1, 2 and 3 forspecifying a plurality of discrete frequency components, signals of eachuser can be properly orthogonalized. When the number of simultaneouslyassigned users is less than the maximum number, as shown in FIG. 7F(4),the base station may increase transmission power of the downlink controlchannel. In addition, hybrid of CDM and FDM can be applied.

FIG. 8A shows a partial block diagram of a mobile terminal used in anembodiment of the present invention. FIG. 8A shows a carrier frequencytuning unit 81, a filtering unit 82, a cyclic prefix (CP) removing unit83, a fast Fourier transform unit (FFT) 84, a CQI measurement unit 85, abroadcast channel (or paging channel) decoding unit 86, a non-specificcontrol channel (part 0) decoding unit 87-0, a non-specific controlchannel decoding unit 87, a specific control channel decoding unit 88and a data channel decoding unit 89.

The carrier frequency tuning unit 81 properly adjusts a center frequencyof a reception band so as to be able to receive a signal of a frequencyblock assigned to the terminal.

The filtering unit 82 filters a received signal.

The cyclic prefix removing unit 83 removes guard interval from areceived signal to extract an effective symbol part from a receivedsymbol.

The fast Fourier transform unit (FFT) performs fast Fourier transform oninformation included in the effective symbol to perform demodulation ofthe OFDM scheme.

The CQI measurement unit 85 measures a received power level of the pilotchannel included in the received signal to feed the measurement resultback to the base station as channel state information CQI. CQI isperformed for each of all resource blocks in the frequency block, andall of them are reported to the base station.

The broadcast channel (or paging channel) decoding unit 86 decodes thebroadcast channel.

When the paging channel is included, it is also decoded.

The non-specific control channel (part 0) decoding unit 87-0 decodesinformation of part 0 in the L1/L2 control channel. By the part 0, itbecomes possible to recognize a transmission format of the non-specificcontrol channel.

The non-specific control channel decoding unit 87 decodes thenon-specific control channel included in the received signal to extractscheduling information. The scheduling information includes informationindicating whether a resource block is assigned to a shared data channeladdressed to the terminal, and information indicating a resource blocknumber when it is assigned, and the like.

The specific control channel decoding unit 88 decodes a specific controlchannel included ion the received signal. The specific control channelincludes information of data modulation, channel coding rate, and HARQon the shared data channel.

The data channel decoding unit 89 decodes the shared data channelincluded in the received signal based on the information extracted fromthe specific control channel. According to the decoding result,acknowledgement (ACK) or negative acknowledgement (NACK) may be reportedto the base station.

FIG. 8B shows a partial block diagram of the mobile terminal like FIG.8A, but, FIG. 8B looks different from FIG. 8A in that each pieces ofcontrol information are concretely shown. Same reference symbolsindicate same elements in FIG. 8A and FIG. 8B. In the figure, “demappingwithin resource block” means extracting information that is mappedlimitedly to one or more resource blocks assigned to a specificcommunication terminal. “Demapping outside resource block” meansextracting information that is mapped over the whole of the frequencyblock including many resource blocks.

FIG. 8C shows elements related to a reception unit of FIG. 8A. Althoughnot essential for the present invention, in the present embodiment,antenna diversity reception using two antennas is performed whenperforming reception. Downlink signals received by two antennas aresupplied to RF reception circuits (81, 82) respectively, guard interval(cyclic prefix) is removed (83), and fast Fourier transform is performed(84). Signals received by each antenna are combined by an antennadiversity combining unit. A signal after combining is supplied to eachdecoding unit shown in FIG. 8A or to a separation unit shown in FIG. 8B.

FIG. 9 is a flowchart showing an operation example according to anembodiment of the present invention. As an example, assuming that a userhaving a mobile terminal UE1 that can perform communication using abandwidth of 10 MHz enters a cell or a sector in which communication isperformed using a bandwidth of 20 MHz. It is assumed that the minimumfrequency band of the communication system is 5 MHz, and that the wholeband is divided into four frequency blocks 1-4 as shown in FIG. 2.

In step S11, the terminal UE1 receives a broadcast channel from the basestation, and checks which frequency block the own terminal can use. Thebroadcast channel may be transmitted using a band of 5 MHz including acenter frequency of the whole band of 20 MHz. Accordingly, any terminalsin which bandwidths that can be received are different can receive thebroadcast channel easily. The broadcast channel permit the user thatperforms communication using the bandwidth of 10 MHz to use acombination of two adjacent frequency blocks such as frequency blocks(1, 2), (2, 3) or (3, 4). All of these may be permitted to use, or usemay be restricted to any of the combinations. As an example, it isassumed that frequency blocks 2 and 3 are permitted to use.

In step S12, the terminal UE1 receives a downlink pilot channel tomeasure received signal quality for the frequency blocks 2 and 3. Themeasurement is performed for each of the many resource blocks includedin each frequency block, so that all of these are reported to the basestation as channel state information CQI.

In step S21, the base station performs frequency scheduling for eachfrequency block based on the channel state information CQI reported fromthe terminal UE1 and other terminals. It is checked and managed by thefrequency block assignment control unit (31 in FIG. 3A) that a datachannel addressed to the UE1 is transmitted from the frequency block 2or 3.

In step S22, the base station generates a control signaling channel foreach frequency block according to scheduling information. The controlsignaling channel includes the non-specific control channel and thespecific control channel.

In step S23, the control channel and the shared data channel aretransmitted from the base station for each frequency block according tothe scheduling information.

In step S13, the terminal UE1 receives a signal transmitted by thefrequency blocks 2 and 3.

In step S14-0, the terminal UE1 recognizes a transmission format of thenon-specific control channel from part 0 of the control channel receivedby the frequency blocks 2 and 3.

In step S14, the terminal separates the non-specific control channelfrom the control channel received by the frequency block 2, decodes itto extract scheduling information. Similarly, the terminal separates thenon-specific control channel from the control channel received by thefrequency block 3, decodes it to extract scheduling information. Anyscheduling information includes information indicating whether aresource block is assigned to a shared data channel addressed to theterminal UE1, and includes information indicating a resource blocknumber when it is assigned, and the like. When any resource block is notassigned to the shared data channel addressed to the own terminal, theterminal UE1 returns to waiting state to wait for receiving the controlchannel. When any resource block is assigned to the shared data channeladdressed to the own station, the terminal UE1 separates the specificcontrol channel included in the received signal and decodes it in stepS15. The specific control channel includes information of datamodulation on the shared data channel, channel coding rate and HARQ.

In step S16, the terminal UE1 decodes the shared data channel includedin the received signal based on information extracted from the specificcontrol channel. Acknowledgment (ACK) or negative acknowledgement (NACK)may be reported to the base station according to the decoding result.After that, similar procedure is repeated.

Embodiment 2

In the first embodiment, the control channel is classified to thespecific control channel that the terminal to which resource block isassigned should decode and demodulate and classified to others, and thespecific control channel is mapped limitedly to the assigned resourceblock, and other control channel is mapped over the whole frequencyband. Accordingly, for the control channel, transmission efficiency canbe improved and the quality can be heightened. However, the presentinvention is not limited to such transmission method examples.

FIG. 7G is a figure showing a mapping example of data channels andcontrol channels according to the second embodiment of the presentinvention. Also in the present embodiment, a base station shown in FIG.3 is used. In this case, process elements shown in FIG. 4B are mainlyused with respect to the control channel. In the present embodiment,specific control information and non-specific control information arenot clearly distinguished, and they are transmitted using the wholeregion of the frequency band over a plurality of resource blocks. Asshown in FIG. 4B, in the present embodiment, error correcting coding isperformed on the whole of the control channel for a plurality of usersas a processing unit. The user apparatus (mobile station, typically)decodes and demodulates the control channel, determines whether the ownstation is assigned, and recovers the data channel transmitted by aspecific resource block according to channel assignment information.

For example, assuming that control information of 10 bits aretransmitted for each of the first to third users UE1, UE2 and UE3 towhich resource blocks are assigned. The whole of the control informationof 30 bits for the three are error correcting coded as a processingunit. When the coding rate (R) is ½, 30×2=60 bits are generated andtransmitted. On the other hand, different from the present embodiment,it can be considered to perform error correcting coding and transmiteach of control information. In that case, control information of 10bits for one user is error correcting coded, 10×2=20 bits are generated,and they are prepared for the three (60 bits in total). The amount ofcontrol information to be transmitted becomes 60 bits for either case.But, according to the present embodiment, since the processing unit oferror correcting coding is three times longer than the other one, it isadvantageous in terms of increasing coding gain (that is, making itharder to cause error). Further, error detection bits (CRC bits and thelike) are added to the whole of the 60 bits in the present embodiment,but, when performing error correcting coding for each user, errordetection bits are added for every 20 bits. Therefore, also from theviewpoint of suppressing increase of overhead due to detection bits, thepresent embodiment is advantageous.

Embodiment 3

FIG. 7H is a figure showing a mapping example of data channels andcontrol channels according to the third embodiment of the presentinvention. Also in the present embodiment, a base station shown in FIG.3 is used, but, as to the control channel, process elements shown inFIG. 4C are mainly used. Also in the present embodiment, althoughspecific control information and non-specific control information arenot clearly distinguished, the control channel is mapped limitedly to aresource block assigned to a user that should receive the controlchannel. For example, a control channel of a first user UE1 is mapped tofirst and second resource blocks RB1 and RB2, a control channel of asecond user UE2 is mapped to third and fourth resource blocks RB3 andRB4, and a control channel of a third user UE3 is mapped to a fifthresource block RB5. Error correcting coding is performed for each user.This point is different from the second embodiment in which the controlchannel of the first to third users are error correcting coded andmapped to resource blocks RB1-RB5 as a whole.

In the present embodiment, the control channel and the data channel arelimited to same resource blocks, but which resource block is assigned toa mobile station is unknown for the mobile station before receiving thecontrol channel. Therefore, it is necessary that each mobile stationshould receive all resource blocks to which the control channel can bemapped so as to demodulate not only the control channel of the ownstation but also control channels of other stations. In the exampleshown in FIG. 7H, the first user UE1 demodulates the control channelsmapped to all of the resource blocks RB1-RB5 to be able to know that theown station is assigned to first and second resource blocks RB1 and RB2.

In the second embodiment, transmission power of the base station isdetermined for a user in the worst environment such that the user in theworst communication environment can receive the control channel with arequired quality. Therefore, it becomes excessive quality for users thatare not in the worst communication environment so that the base stationalways needs to consume surplus power. However, in the third embodiment,since processing such as error correcting coding and transmission bandis limited to resource blocks of each user, transmission power controlcan be also performed for each user. Therefore, it becomes unnecessaryto consume redundant power in the base station. In addition, since theresource block is assigned to a user in a good channel state, thecontrol channel is transmitted in such a good channel state so thatquality of the control channel can be improved.

Embodiment 4

FIG. 7I is a figure showing a mapping example of data channels andcontrol channels according to a fourth embodiment of the presentinvention. Also in the present embodiment, a base station shown in FIG.3 is used, but, process elements on the control channel become thoseshown in FIG. 4C. Also in the present embodiment, although specificcontrol information and non-specific control information are not clearlydistinguished, the control channel is error correcting coded for eachuser so that transmission power is determined like the third embodiment.However, the control channel is not only mapped to resource blocksassigned to a user that should receive the control channel but alsomapped to other resource blocks in a distributed manner. Also in thismanner, the control channel can be transmitted.

By the way, in the first to fourth embodiments, when mapping the controlchannel to a plurality of resource blocks in a distributed manner, it isnot essential to map the control channel into all of the resource blocksin a given frequency band. For example, the control channel may bemapped only to odd-numbered resource blocks RB1, RB3, . . . in the givenfrequency band, or may be mapped only to even-numbered resource blocks.The control channel may be mapped limitedly to any proper resourceblocks known between the base station and the mobile station.Accordingly, search range used when the mobile station extractsassignment information of the own station can be properly narrowed.

Embodiment 5

As mentioned above, in the second embodiment, transmission power of thebase station is determined for a user in the worst communicationenvironment so that the base station should always consume surpluspower. However, if communication environments of many users aresimilarly good, such fear can be overcome. Therefore, in a communicationenvironment in which comparable quality can be obtained for a pluralityof users, the method described in the second embodiment is advantageous.From this viewpoint, in the fifth embodiment of the present invention,user apparatuses in a cell are properly grouped and use frequency bandis divided for each group.

FIG. 7J shows a schematic diagram for explaining the fifth embodiment ofthe present invention. In the example shown in the figure, three groupsare prepared according to a distance from the base station, in whichresource blocks RB1-RB3 are assigned to the group 1, resource blocksRB4-RB6 are assigned to the group 2, and resource blocks RB7-RB9 areassigned to the group 3. The prepared number of groups and the number ofresource blocks are merely examples, and any proper number may be used.After being grouped, each of the various methods described in the firstto fourth embodiments may be performed. By grouping the users andfrequency bands, difference of reception quality among users can bedecreased. Accordingly, the problem (problem feared in the secondembodiment) that surplus amount of transmission power is consumed in thebase station due to the user in the worst environment can be effectivelyaddressed. In addition, also in the third embodiment, by performinggrouping like the present embodiment, transmission powers of controlchannels become comparable in the same group, so that it becomesadvantageous from the viewpoint for stabilizing operation of a basestation transmitter, and the like.

In the example shown in the figure, for the sake of simplifying theexplanation, three groups are prepared according to the distance fromthe base station. However, grouping can be performed not only based onthe distance but also based on channel quality indicator (CQI). CQI maybe measured as any proper amount that is known to this technical fieldsuch as SIR and SINR and the like.

Embodiment 6

The non-specific control channel (including part 0) is informationnecessary for all users, and the data channel is decoded based on thenon-specific control channel. Thus, error detection (CRC) coding andchannel coding are performed on the non-specific control channel. In thesixth embodiment of the present invention, concrete examples of theerror detection coding and the channel coding are explained. FIG. 4E isa figure corresponding to a configuration in which channel coding isperformed on L1/L2 control information (part 0) and L1/L2 controlinformation (part 2 a and 2 b) separately (includingcoding/spreading/data modulation units 41, 42-A for each controlinformation). In the following, alternative configurations of this aredescribed.

FIG. 10A shows a case in which part 0 and parts 2 a and 2 b are errordetection coded as a whole, and, part 0, and parts 2 a and 2 b areseparately channel coded. Communication terminals UE1 and UE2 performerror detection for the part 0, and parts 2 a and 2 b as a whole, anduse a L1/L2 control channel for the own communication terminal fromparts 2 a and 2 b based on the part 0.

Since error detection (CRC) code may become larger than control bits ofpart 0, in this case, overhead of error detection coding can bedecreased.

FIG. 10B indicates a case in which part 0, and, parts 2 a and 2 b areseparately error detection coded, and part 0, and, parts 2 a and 2 b areseparately channel coded. Although the overhead becomes larger comparedwith the case of FIG. 10A, there is an advantage in that, when errordetection for part 0 fails, it becomes unnecessary to perform processingfor parts 2 a and 2 b.

FIG. 10C shows a case in which part 0 and parts 2 a and 2 b are errordetection coded as a whole, and part 0 and parts 2 a and 2 b are channelcoded as a whole. In this case, although information of part 0 cannot beextracted unless part 0 and parts 2 a and 2 b are decoded together,there is an advantage in that efficiency of channel coding rateincreases.

In FIGS. 10A-10C, although error detection coding and channel coding forpart 0 and part 2 a and 2 b are described, they can be similarly appliedto non-specific control channels other than the parts 2 a and 2 b.

Embodiment 7

FIG. 10D shows a method example for decreasing information amount ofuplink data transmission related information. In step S1, a downlinkL1/L2 control channel is transmitted from the base station. As mentionedbefore (especially, as described being related to FIG. 7F), a pluralityof pieces of control information for a plurality of communicationterminals are multiplexed and transmitted (assuming that the usermultiplexing number is N, for the sake of convenience). Eachcommunication terminal demodulates a plurality of L1/L2 control channelsaddressed to own and other communication terminals. For example, it isassumed that a control channel including UE-ID of own terminal is mappedto a X-th position in N. In this case, the user apparatus performsdemodulation N times at most so as to find out a non-specific controlchannel addressed to the own apparatus mapped to the X-th position, andascertain assignment content (which resource block can be used for theown terminal, and the like) of the own terminal based on assignmentinformation included in that.

In step S2, using the assigned RB that is assigned, a packet (t=TTI1) ofuplink is transmitted to the base station, for example. “t=TTI1”indicates time.

In step S3, the base station receives the uplink data channel D(t=TTI1),decodes it to determine presence or absence of an error. Thedetermination result is represented by ACK or NACK. The base stationshould report the determination result to the source communicationterminal. The base station reports the determination result to thecommunication terminal using the L1/L2 control channel. Thisdetermination result (transmission confirmation result) belongs to part1 of the uplink data transmission related information according to theclassification of FIG. 5A. Since the base station also receives uplinkchannels from various communication terminals, the base station reportstransmission confirmation information to all of the communicationterminals respectively. Therefore, for distinguishing these pieces ofinformation with each other, user identification information (ID) isadded to all of part 1 (ACK/NACK) of the uplink data transmissionrelated information in the downlink L1/L2 control channel, so that eachcommunication terminal can ascertain, without fail, transmissionconfirmation information (ACK/NACK) for the uplink data channel that wastransmitted by the own terminal in the past.

However, in the present embodiment, from the viewpoint of decreasing thecontrol information amount, transmission of the downlink L1/L2 controlchannel is performed without adding identification information to eachpiece of the information of part 1 of each communication terminal.Instead of that, correspondence relationship between the assignmentnumber X used when mapping information of part 2 and information of part1 is maintained for each communication terminal. For example, when amultiplexing method shown in FIG. 7F(1) is performed, assuming thatassignment number 3 (X=3) is used for reporting information of part 2 tothe communication terminal UE1 (third one in the multiplexing number N).In this case, by demodulating the resource information of the assignmentnumber 3, a resource block of the uplink data channel is specified, sothat the uplink data channel is transmitted by the resource block. Theinformation (ACK/NACK) of the part 1 for the uplink data channel isdescribed in the resource of assignment number 3 in the downlink L1/L2control channel transmitted at t=TT1+α, in which α is time set forreturning the transmission confirmation information. In step S3, such aL1/L2 control channel is transmitted to the communication terminal.

In step S4, each communication terminal reads information on part 1based on the assignment number X and the predetermined period α to checkwhether it should retransmit data D(t=TTI1) that was transmitted att=TTI1.

Accordingly, in the present embodiment, by maintaining one to onecorrespondence relationship between the assignment number that was usedin step S1 and the assignment number used in step S3, the base stationdoes not need to specify that the part (ACK/NACK) of the uplink datatransmission related information is addressed to which communicationterminal individually. Thus, according to the present method,information amount of the downlink L1/L2 control channel generated instep S22 in FIG. 9 can be decreased. Assuming that resources for uplinkdata channel are assigned to M communication terminals at a time oft=TTI1, the assignment number X is 1, . . . , M, and also, the number ofassignment information (part 2) of the uplink data transmission relatedinformation, and the number of destinations to which transmissionconfirmation information (part 1) should be sent at a later time t=TTI+αare commonly M. Therefore, it is always possible to maintain the one toone correspondence relationship for the assignment number X.

Embodiment 8

FIG. 10E is a figure showing an operation example when frequency hoppingis performed. The frequency band assigned to the communication system is20 MHz which includes four frequency blocks each having a minimumbandwidth of 5 MHz. In the example shown in the figure, thecommunication system can accommodate 40 users that can performcommunication using a band of 5 MHz, 20 users that can performcommunication using a band of 10 MHz, and 10 users that can performcommunication using a band of 20 MHz.

The user that can perform communication using the band of 20 MHz canalways use all of the frequency blocks 1-4. However, in the 40 usersthat can perform communication only with the band of 5 MHz, first totenth users are permitted to use only frequency block 1 at a time t,permitted to use only frequency block 2 at a time t+1, and permitted touse only frequency block 3 at a time t+2. Eleventh to twentieth usersare permitted to use frequency blocks 2, 3 and 4 at times t, t+1 and t+2respectively. Twenty first to thirtieth users are permitted to usefrequency blocks 3, 4 and 1 at times t, t+1 and t+2. Thirty first tofortieth users are permitted to use frequency blocks 4, 1 and 2 at timest, t+1 and t+2. In addition, in the 20 users that can performcommunication only with the band of 10 MHz, first to tenth users arepermitted to use only frequency blocks 1 and 2 at a time t, permitted touse only frequency blocks 3 and 4 at a time t+1, and permitted to useonly frequency blocks 1 and 2 at a time t+2. Eleventh to twentieth usersare permitted to use frequency blocks 3 and 4, 1 and 2, and 3 and 4 attimes t, t+1 and t+2 respectively.

Such a frequency hopping pattern is reported to each user beforehand bya broadcast channel or other methods. In this case, some patters aredefined beforehand as frequency hopping patterns, and a pattern numberindicating which pattern is used in the patters is reported to a user,so that the frequency hopping pattern can be reported to the user with asmall number of bits. When there are some choices in usable frequencyblocks like the present embodiment, it is desirable to change usablefrequency block after starting communication from the viewpoint ofequalizing communication quality among users and among frequency blocks.For example, if the frequency hopping is not performed like the presentembodiment, a particular user should always perform communication in badquality when difference of superiority or inferiority of communicationquality among frequency blocks is large. By performing frequencyhopping, although communication quality is bad at a time, it can beexpected that it becomes good at another time.

In the example shown in the figure, although a frequency hopping patternin which frequency blocks of 5 MHz and 10 MHz shift to the right sideone by one is shown, other various hopping patters may be used. This isbecause, even though any hopping pattern is adopted, it is onlynecessary that the pattern is known in the transmission side and thereception side.

Embodiment 9

In the ninth embodiment of the present invention described below, amethod for transmitting a paging channel in addition to the controlsignaling channel is described.

FIG. 11 is a figure showing a flowchart (left side) of an operationexample and frequency bands (right side) of an embodiment of the presentinvention. In step S1, a broadcast channel is transmitted from the basestation to users under the base station. As shown in FIG. 11(1), thebroadcast channel is transmitted using a minimum bandwidth including acenter frequency of the whole frequency band. Broadcast informationreported by the broadcast channel includes correspondence relationshipbetween frequency bands that users can receive and usable frequencyblocks.

In step S2, a user (UE1, for example) enters a waiting state for aspecified frequency block (frequency block 1, for example). In thiscase, the user UE1 adjust the band of reception signal such that it canreceive a signal of the frequency block 1 that is permitted to use. Inthe present embodiment, not only a control signaling channel for theuser UE1 but also a paging channel for the user UE1 are transmittedusing the frequency block 1. When it is checked that the user UE1 ispaged by the paging channel, the flow goes to step S3.

In step S3, the data channel is received according to schedulinginformation using the specified frequency block. The user UE1 returns tothe waiting state again after that.

FIG. 12 is a figure showing a flowchart (left side) of another operationexample and frequency bands (right side) of an embodiment of the presentinvention. In step S1, like the above-mentioned example, a broadcastchannel is transmitted from the base station to users under the basestation, and the broadcast channel is transmitted using a minimumbandwidth including a center frequency of the whole frequency band (FIG.12 (1)). Like the example of FIG. 11, it is assumed that the usablefrequency block is the frequency block 1.

In step S2, the user UE1 enters a waiting state. Different from theabove example, the user UE1 does not adjust the band of reception signalat this time. Therefore, the user UE1 waits for a paging channel usingthe band same as that for receiving the broadcast channel (FIG. 12 (2)).

In step S3, after the paging channel is identified, the terminal movesto the frequency block 1 that is assigned to the own station, andreceives the control signaling channel to perform communicationaccording to scheduling information (FIG. 12 (3)). The user UE1 returnsto the waiting state again after that.

In the example shown in FIG. 11, the terminal quickly moves to thefrequency block 1 at the time of waiting. But, in the example shown inFIG. 12, the terminal does not move at that time, but moves to thefrequency block 1 after paging of the own terminal is identified. In theformer method, each of various users waits for a signal using afrequency block assigned to each user. On the other hand, in the lattermethod, every user waits for a signal using a same band. Therefore, theformer method may be preferable compared with the latter in thatfrequency resources can be used evenly. On the other hand, neighboringcell search for checking necessity of handover is performed using theminimum bandwidth of the center of the whole band. Thus, from theviewpoint of decreasing the number of times of frequency tuning in theterminal, it is desirable to match the band when used in waiting to theband for cell search like the example shown in FIG. 12.

Embodiment 10

By the way, it is desirable to perform link adaptation from theviewpoint of improving reception signal quality of the control channel.In the tenth embodiment of the present invention, as a method forperforming link adaptation, transmission power control (TPC) andadaptive modulation and coding (AMC) control are used. FIG. 13 shows amanner in which transmission power control is performed, and it isintended to achieve required quality in the reception side bycontrolling transmission power of the downlink channel. Moreparticularly, since it is predicted that channel state for a user 1 farfrom the base station is bad, the downlink channel is transmitted usinga large transmission power. In contrast, it is predicted that channelstate is good for a user 2 near the base station. In this case, iftransmission power of the downlink channel to the user 2 is large,reception signal quality for the user 2 may be good, but interferencebecomes large for other users. Since channel state for the user 2 isgood, required quality can be ensured even though transmission power issmall. Therefore, in this case, the downlink channel is transmitted witha relatively small transmission power. When transmission power controlis performed solely, the modulation scheme and the channel coding schemeare kept constant, and a combination known to the transmission side andthe reception side is used. Therefore, it is not necessary to separatelyreport a modulation scheme and the like for demodulating a channel inthe transmission power control.

FIG. 14 shows a manner in which adaptive modulation and coding controlis performed, and in which it is intended to achieve required quality inthe reception side by adaptively changing both or one of the modulationscheme and the coding scheme according to good or bad of the channelstate. More particularly, if transmission power from the base station isconstant, since it is predicted that channel state of a user 1 far fromthe base station is bad, the number of modulation levels of multilevelmodulation is set to be small and/or the channel coding rate is set tobe small. In the example shown in the figure, QPSK is used as amodulation scheme for the user 1, and information of 2 bits aretransmitted per 1 symbol. On the other hand, it is predicted thatchannel state for the user 2 located near the base station is good, sothat the number of modulation levels is set to be large and/or thechannel coding rate is set to be large. In the example shown in thefigure, 16 QAM is used as a modulation scheme for the user 2, andinformation of 4 bits is transmitted per 1 symbol. Accordingly, requiredquality is achieved for a user in bad channel state by increasingreliability, and throughput can be improved while maintaining requiredquality for a user in a good channel state. In the adaptive modulationand coding control, when demodulating a received channel, information ofa modulation scheme performed on the channel, coding scheme, number ofsymbols and the like is necessary. Thus, it is necessary that theinformation is reported to the reception side using some way. Inaddition, since the number of bits that can be transmitted per onesymbol is different according to good or bad of the channel state,information can be transmitted with a small number of symbols when thechannel state is good, but when it is not good, a large number ofsymbols are necessary.

In the tenth embodiment of the present invention, transmission powercontrol is performed for a non-specific control channel thatnon-specific users should decode, and one or both of transmission powercontrol and adaptive modulation and coding control is performed for aspecific control channel that a specific user to which a resource blockis assigned decodes. In particular, following three methods can beconsidered.

(1) TPC-TPC

In the first method, transmission power control is performed for thenon-specific control channel, and also only transmission power controlis performed for the specific control channel. Since modulation schemeand the like are fixed in transmission power control, when a channel isproperly received, it can be demodulated without prior notification ofmodulation scheme and the like. Since the non-specific control channelis distributed over the whole frequency blocks, the non-specific controlchannel is transmitted using a same transmission power over the wholefrequency range. On the other hand, a specific control channel for auser only occupies a specific resource block for the user. Therefore,transmission power of the specific control channel may be adjustedindividually such that received signal quality becomes good for eachuser to which the resource block is assigned. For example, in theexamples shown in FIGS. 7A and B, the non-specific control channel maybe transmitted using transmission power P₀, a specific control channelof the user 1 (UE1) may be transmitted using transmission power P₁suitable for the user 1, a specific control channel of the user 2 (UE2)may be transmitted using transmission power P₂ suitable for the user 2,and a specific control channel of the user 3 (UE3) may be transmittedusing transmission power P₃ suitable for the user 3. By the way, thepart of the shared data channel may be transmitted with a same ordifferent transmission power P_(D).

As mentioned above, the non-specific control channel should be decodedby all of the non-specific users. However, main purpose for transmittingthe control channel is to report that there is data to be received andto report scheduling information and the like to a user to which aresource block is actually assigned. Therefore, transmission power whentransmitting the non-specific control channel may be adjusted such thatrequired quality is satisfied for the user to which the resource blockis assigned. For example, in the examples shown in FIGS. 7A and B, whenall of the users 1, 2 and 3 are located near the base station,transmission power P₀ of the non-specific control channel may be set tobe relatively small. In this case, users other than the users 1, 2 and 3located at an end of the cell, for example, may not be able to decodethe non-specific control channel properly. But, since the users are notassigned a resource block, there is no actual harm.

(2) TPC-AMC

In the second method, transmission power control is performed for thenon-specific control channel, and only adaptive modulation and codingcontrol is performed for the specific control channel. When the AMCcontrol is performed, generally, it is necessary that the modulationscheme and the like are reported beforehand. In the present method,information such as the modulation scheme and the like for the specificcontrol channel is included in the non-specific control channel.Therefore, each user receives the non-specific control channel first,decodes and demodulates it to determine presence or absence of dataaddressed to the own station. If the data exists, in addition toextracting scheduling information, the user extracts information on themodulation scheme, coding scheme and the number of symbols and the likethat are applied to the specific control channel. Then, the specificcontrol channel is demodulated according to the scheduling informationand information of the modulation scheme and the like, information ofthe modulation scheme and the like for the shared data channel isobtained, so that the shared data channel is demodulated.

It is not so required to transmit the control channel with highthroughput compared with the shared data channel. Therefore, when AMCcontrol is performed for the non-specific control channel, the totalnumber of combinations of modulation schemes and the like can be lessthan the total number of modulation schemes and the like for the shareddata channel. For example, as a combination of AMC for the non-specificcontrol channel, the modulation scheme may be fixed to QPSK, and thecoding rate may be changed like ⅞, ¾, ½ and ¼.

According to the second method, quality of the specific control channelcan be made good while maintaining quality of the non-specific controlchannel to be equal to or greater than a predetermined level over thewhole users. This is because the specific control channel is mapped to aresource block in a good channel state for each of specificcommunication terminals, and proper modulation scheme and/or codingscheme is used. In the control channel, by performing adaptivemodulation and coding control on a part of the specific control channel,reception quality of the part can be improved.

By the way, the number of combinations of modulation schemes and channelcoding rates may be limited to very small, so that demodulation may betried for every combination in the reception side. Content by whichdemodulation can be performed well is adopted finally. Accordingly, eventhough information on modulation scheme and the like is not reportedbeforehand, AMC control can be performed to some extent.

(3) TPC-TPC/AMC

In the third method, transmission power control is performed for thenon-specific control channel, and both of transmission power control andadaptive modulation and coding control are performed for the specificcontrol channel. As mentioned above, when AMC control is performed, itis necessary that modulation scheme and the like is reported beforehandas a general rule. In addition, it is desirable that the total number ofcombinations of modulation schemes and channel coding rates is largefrom the viewpoint of maintaining required quality even when there islargely changing fading. However, when the total number is large,determining processes for the modulation scheme and the like becomecomplicated, and the amount of information necessary for notificationbecomes large so that calculation load and overhead become large. In thethird method, transmission power control is used in addition to the AMCcontrol so that required quality is maintained by both controls.Therefore, it is not necessary to compensate for all of the largelychanging fading only by AMC control. In particular, modulation schemeand the like that reaches the vicinity of required quality is selected,so that required quality can be maintained by adjusting transmissionpower under the selected modulation scheme and the like. Therefore, thetotal number of combinations of the modulation schemes and the channelcoding schemes may be limited to small.

In any of the above methods, since only transmission power control isperformed for the non-specific control channel, the user can easilyobtain control information while required quality is maintained.Different from AMC control, since information transmission amount perone symbol is unchanging, transmission can be performed easily using afixed format. Since the non-specific control channel is distributed overthe whole region of the frequency blocks or over many resource blocks,frequency diversity effect is large. Therefore, it can be expected thatrequired quality is sufficiently achieved by simple transmission powercontrol such as one in which long periodic average level is adjusted. Bythe way, it is not essential for the present invention that onlytransmission power control is performed for the non-specific controlchannel. For example, the transmission format used for the non-specificcontrol channel may be controlled in a low speed using a broadcastchannel.

By including AMC control information (information for specifying themodulation scheme and the like) for the specific control channel in thenon-specific control channel, AMC control can be performed for thespecific control channel. Thus, transmission efficiency and quality canbe improved for the specific control channel. Although the number ofsymbols necessary for the non-specific control channel is almostconstant, the number of symbols necessary for the specific controlchannel is different according to content of AMC control and the numberof antennas and the like. For example, assuming that the number ofnecessary symbols is N when the channel coding rate is ½ and the numberof antenna is 1, the number of necessary symbols increases to 4N whenthe channel coding rate is ¼ and the number of antennas is 2.Accordingly, even though the number of necessary symbols for the controlchannel changes, the control channel can be transmitted by a simplefixed format as shown in FIGS. 7A and B in the present embodiment.Content of change of the number of symbols is not included in thenon-specific control channel, and it is included only in the specificcontrol channel. Therefore, by changing occupation ratio of the specificcontrol channel and the shared data channel in a specific resourceblock, such a change of the number of symbols can be flexible dealtwith.

As mentioned above, although preferred embodiments of the presentinvention are described, the present invention is not limited to those,and various variations and modifications may be made without departingfrom the scope of the present invention. For the sake of explanation,although the present invention is described by being divided to someembodiments, the division to each embodiment is not essential for thepresent invention, and equal to or greater than two embodiments may beused as necessary.

The present international application claims priority based on Japanesepatent application No. 2006-10496, filed in the JPO on Jan. 18, 2006 andthe entire contents of the Japanese patent application is incorporatedherein by reference.

The present international application claims priority based on Japanesepatent application No. 2006-127987, filed in the JPO on May 1, 2006 andthe entire contents of the Japanese patent application is incorporatedherein by reference.

The present international application claims priority based on Japanesepatent application No. 2006-272347, filed in the JPO on Oct. 3, 2006 andthe entire contents of the Japanese patent application is incorporatedherein by reference.

The present international application claims priority based on Japanesepatent application No. 2006-298312, filed in the JPO on Nov. 1, 2006 andthe entire contents of the Japanese patent application is incorporatedherein by reference.

The invention claimed is:
 1. A transmission apparatus comprising: afrequency scheduling unit configured to assign at least one resourceblock to individual communication terminals, wherein a frequency bandprovided to a communication system includes a plurality of frequencyblocks each of which includes a plurality of resource blocks; and afirst generation unit configured to generate a data channel for acommunication terminal to which at least one resource block is assignedin the frequency scheduling unit; a second generation unit configured togenerate a specified control channel for a communication terminal, on aterminal-by-terminal basis, to which at least one resource block isassigned in the frequency scheduling unit; a third generation unitconfigured to generate an unspecified control channel common tocommunication terminals to which at least one resource block is assignedin the frequency scheduling unit; a fourth generation unit configured togenerate a broadcast channel including broadcast information to bereported to a communication terminal; a multiplexing unit configured toarrange the broadcast channel generated in the fourth generation unit ona frequency block which includes a center frequency among the pluralityof frequency blocks included in the frequency band provided to thecommunication system, and arrange the unspecified control channelgenerated in the third generation unit, at least one specified controlchannel generated in the second generation unit and at least one datachannel generated in the first generation unit over the plurality offrequency blocks included in the frequency band provided to thecommunication system: and a transmission unit configured to transmit anoutput signal of the multiplexing unit, wherein the number of symbols ina part which includes at least one specified control channel generatedin the second generation unit is variable, and the unspecified controlchannel generated in the third generation unit includes informationrelated to the number of symbols in a part which includes at least onespecified control channel generated in the second generation unit. 2.The transmission apparatus as claimed in claim 1, wherein the specifiedcontrol channel generated in the second generation unit includesinformation related to a data modulation scheme.
 3. The transmissionapparatus as claimed in claim 1, wherein the specified control channelgenerated in the second generation unit includes information related toa coding scheme.
 4. The transmission apparatus as claimed in claim 1,wherein the specified control channel generated in the second generationunit includes information related to hybrid retransmission control. 5.The transmission apparatus as claimed in claim 1, wherein the specifiedcontrol channel generated in the second generation unit includesprecoding information for use in a MIMO scheme.
 6. The transmissionapparatus as claimed in claim 1, wherein the multiplexing unit timemultiplexes at least one data channel generated in the first generationunit onto the unspecified control channel generated in the thirdgeneration unit and at least one specified control channel generated inthe second generation unit.
 7. The transmission apparatus as claimed inclaim 1, wherein the multiplexing unit arranges a paging channel in asimilar way to the data channel.
 8. A transmission method comprising thesteps of: assigning at least one resource block to individualcommunication terminals, wherein a frequency band provided to acommunication system includes a plurality of frequency blocks each ofwhich includes a plurality of resource blocks; and generating a datachannel for a communication terminal to which at least one resourceblock is assigned; generating a specified control channel for acommunication terminal, on a terminal-by-terminal basis, to which atleast one resource block is assigned; generating an unspecified controlchannel common to communication terminals to which at least one resourceblock is assigned; generating a broadcast channel including broadcastinformation to be reported to a communication terminal; arranging thebroadcast channel on a frequency block which includes a center frequencyamong the plurality of frequency blocks included in the frequency bandprovided to the communication system, and arranging the unspecifiedcontrol channel, at least one specified control channel and at least onedata channel over the plurality of frequency blocks included in thefrequency band provided to the communication system; and transmitting anoutput signal from the step of arranging, wherein the number of symbolsin a part which includes at least one specified control channelgenerated in the step of generating the specified control channel isvariable, and the unspecified control channel generated in the step ofgenerating the unspecified control channel includes information relatedto the number of symbols in a part which includes at least one specifiedcontrol channel generated in the step of generating the specifiedcontrol channel.
 9. The transmission method as claimed in claim 8,wherein the specified control channel generated in the step ofgenerating the specified control channel includes information related toa data modulation scheme.
 10. The transmission method as claimed inclaim 8, wherein the specified control channel generated in the step ofgenerating the specified control channel includes information related toa coding scheme.
 11. The transmission method as claimed in claim 8,wherein the specified control channel generated in the step ofgenerating the specified control channel includes information related tohybrid retransmission control.
 12. The transmission method as claimed inclaim 8, wherein the specified control channel generated in the step ofgenerating the specified control channel includes precoding informationfor use in a MIMO scheme.
 13. The transmission method as claimed inclaim 8, wherein, in the step of arranging, at least one data channel istime-multiplexed onto the unspecified control channel and at least onespecified control channel.
 14. The transmission method as claimed inclaim 8, wherein, in the step of arranging, a paging channel is arrangedin a similar way to the data channel.